The present invention relates to a signal processing device and an image input device for an image signal formed into one chip which includes a MOS type solid image sensing device.
In recent years, the MOS type solid image sensing device has been used as various image input devices. In particular, an image sensing element of a type referred to as a CMOS type image sensing element which is fabricated by the CMOS manufacturing technique has widely been used. Most of integrated circuit elements other than the image sensing element are also fabricated by the same CMOS manufacturing technique as in the CMOS type image sensing device. In a CMOS type image sensing device chip, therefore, it is possible to integrate, on the same chip, other integrated circuit elements, particularly, a digital signal processing circuit and a memory element as well as the image sensing element. In recent years, an image input device which is small-sized and consumes less power has been required.
FIG. 1 shows an example of a structure of a conventional image input chip fabricated to meet such a demand. An image input chip 10 comprises an image input section 11 and a signal processing section 12.
The image input section 11 includes an array of pixel 14 in which a plurality of pixels 13 having a CMOS type photoelectric converting element for converting incident light into an electric signal (an analog signal), for example, are arranged in a matrix, and a plurality of analog to digital (A/D) converters 15 for converting the analog signal converted by the pixels 13 into a digital signal and outputting the digital signal.
The signal processing section 12 is provided for the A/D converter 15 by one to one, and includes a plurality of processing elements (PE) 16 for carrying out a signal processing by using the digital signals output from the A/D converters 15 and a signal output circuit 17 for outputting the result of the processing performed by the PE 16 to the outside of the chip. Each of the PEs 16 in the signal processing section 12 carries out a signal processing according to an instruction generated by a controller 18.
The analog signal converted by the pixel 13 in the array of pixel 14 is sequentially converted into a digital signal by the A/D converters 15 in a row unit, and is transmitted to the signal processing section 12. In the signal processing section 12, a signal processing is carried out in parallel according to the instruction generated by the controller 18 by means of the PEs 16. The processed signal is output from the signal output circuit 17 to the outside of the chip.
In the image input chip shown in FIG. 1, thus, the image input section and the signal processing section are formed on the same chip. Therefore, as compared with the case in which the signal processing is carried out with a signal processing chip other than the image input chip, the system size can be reduced and an inexpensive image input system can be implemented.
In the image input system in which the image input chip and the signal processing chip are divided, moreover, it is necessary to drive a comparatively great load capacity attached to a wiring when a signal is to be transmitted from the image input chip to the signal processing chip. For this reason, consumed power has been increased. In the chip shown in FIG. 1, however, it is not necessary to consume power for signal transmission between the chips. Consequently, an image input system having low power consumption can be implemented.
However, the conventional example shown in FIG. 1 has the following problems. More specifically, when the PEs 16 are arranged for each column of the array of pixel 14, the width in the column direction of the pixel 13 is small, that is, approximately several μm. Therefore, the circuit scale and the signal processing capability of the PE 16 which can be arranged are limited, resulting in a low signal processing speed. In general, the amount of data to be processed is large in an image processing. Therefore, if the signal processing speed is low, troubles are practically made. Thus, the use of the image input device is restricted.